Which design considerations are essential for effective LEV performance?

• A. Aesthetic appearance of the hood.
• B. Proximity to cafeteria.
• C. Capture velocity at the source, ducting layout, and filter efficiency.
• D. Brand of fan motor only.

Answer: (C)

Local exhaust ventilation effectiveness comes from pulling contaminants right at the source and moving them through a well-designed path to filtration or exhaust. The most important design elements are capture velocity at the source, the ducting layout, and filter efficiency. Capture velocity at the source ensures the contaminated air is drawn into the hood before it can escape into the room, which prevents exposure and keeps the system performing as intended. If that velocity is insufficient or the hood isn’t well positioned, contaminants will disperse into the workspace, undermining protection. The ducting layout matters because it determines pressure losses and the potential for leaks or excessive backpressure; a poorly laid out system reduces actual flow at the hood, wastes energy, and can allow leaks that bypass filtration. Filter efficiency is essential to remove contaminants from the airstream before discharge or recirculation, directly affecting air quality and compliance. The other aspects mentioned—appearance of the hood, proximity to the cafeteria, or the brand of the fan motor—don’t directly govern how well the system captures, transports, and cleans the contaminant, so they don’t drive effectiveness.